In a variety of surgical procedures on the eye, it is desirable or necessary to prevent the eye from moving. Examples include corneal refractive surgery, corneal laser surgery (e.g., with the 193 nm excimer laser), and radial keratotomy. Currently, ophthalmologists use one of a variety of types of instruments to stabilize the eye during such procedures.
One such device is shown in U.S. Pat. No. 5,009,660 (Clapham). The Clapham device utilizes a vacuum ring carded at the end of a handle which extends away from the vacuum ring at an angle. The vacuum ring can be secured to the eye around the cornea, permitting the physician to substantially prevent movement of the eye.
U.S. Pat. No. 4,718,418 (L'Esperance) uses a vacuum ring which can be placed on the eye, the vacuum ring being rigidly connected to an external piece of equipment (in this case, a laser used in treatment of the eye).
My prior patent, U.S. Pat. No. 5,171,254, shows an eye fixation device that includes a speculum securable against the patient's bony orbit, and a separate fixation ring attachable to the patient's eye (typically by vacuum). A mechanism is provided for adjustably attaching the ring to the speculum to prevent movement of the eye once the proper position of the eye for the procedure is obtained.
In some ophthalmic procedures, such as corneal excimer laser surgery, it is desirable to first remove the epithelium layer of the cornea. This can be accomplished by merely mechanically scraping this thin layer off with a suitable device. Alternately, in an excimer laser procedure the laser itself can be used to remove the epithelial layer. This layer is of varying thickness of different patients, however, and its thickness (typically on the order of about 45-55 microns) is not easy to measure. Thus, it can be difficult to estimate the length of time necessary for the laser to remove just this thin layer.
It has been discovered, however, that epithelial cells of the human cornea fluoresce (green) when exposed to the 193 nm light of the excimer laser. Thus, with the operating room lights turned off, the physician can observe this fluorescence as the laser ablates the epithelium, arid can stop the laser ablation when the fluorescence disappears. With all room lights turned off, however, it can be difficult for the physician to monitor the position of the eye just before turning the laser on and when the epithelium has been nearly entirely ablated; it is also difficult to confirm that the eye has not moved during the procedure.